Analysis of Dam Overtopping by Considering Hydraulic and Hydrological Uncertainties

Document Type : Research Article


1 PhD Candidate, School of Civil Engineering, Iran University of Science and Technology

2 Assistant Professor, School of Civil Engineering, Iran University of Science and Technology


Adequate determination of dam overtopping risk by considering random variables uncertainty is an important issue in the design of earthfill dam. Therefore, ignoring these uncertainties cause overestimation or underestimation of dam height. Uncertainties of rainfall and flood have more effect on overtopping risk. In this study, flood hydrograph was generated by considering uncertainness of rainfall and rainfall-runoff parameters with using developed model named RPG (Rain Pattern Generator) and HEC1 models. In addition, overtopping risk of Jamishan dam was estimated by using the Monte Carlo simulation (MCs). The effect of main variables such as spillway width, dam height and normal water level on risk of dam overtopping was evaluated by considering related variants. Results show that average variation rate of dam overtopping risk was 0.03 based on unit variation of spillway width. Also average variation rate of overtopping risk was respectively 3.1 and 1.56 based on unit variation of normal water level and dam height. Therefore, variation of flood control volume is more effective on risk of dam overtopping than spillway capacity.


[1]     Afshar A. and Marino M.A. (1990). "Optimizing spillway capacity with uncertainty in flood estimator", Journal of Water Resources Planning and Management, 116 (l), pp. 71–84.
[2]     Afshar A., Barkhordary A., and Marino M.A. (1994). "Optimizing river diversion under hydraulic and hydrologic uncertainties", Journal of Water Resources Planning and Management, 120 (1), pp. 36–47.
[3]     Afshar A., Rasekh A. and Afshar M.H. (2009). "Risk-based optimization of large flood-diversion systems using genetic algorithms", Engineering Optimization, Vol. 41, No. 3, pp. 259-273.
[4]     Goodarzi E., Mirzaei M., Shui L.T. and Ziaei M. (2011). "Evaluation dam overtopping risk based on univariate and bivariate flood frequency analysis". Hydrol., Earth Syst. Sci. Discuss., 8, pp. 9757–9796.
[5]     Gui S., Zhang R. and Xue X. (1998). "Overtopping reliability models for river levee", Journal of Hydraulic Engineering, Vol. 124, No. 12, pp. 1227-1234.
[6]     Gui S., Zhang R. and Wu J. (1998). "Simplified dynamics reliability models for hydraulic desing", Journal of Hydraulic Engineering, Vol. 124, No. 3, pp. 329-333.
[7]     Hsu Y.C., Tung Y.K. and Kuo J.T. (2011). "Evaluation of dam overtopping probability induced by flood and wind", Stoch. Environ. Res. Risk Assess., 25, pp. 35-49.
[8]     International Commission on Large Dams (ICOLD), (1973). Lessons from dam incidents (reduced edition). ICOLD, Paris.
[9]     Kuo J.T., Yen B.C., Hsu Y.C. and Lin H.F., (2007). "Risk analysis for dam overtopping—Feitsui reservoir as a case study", Journal of Hydraulic Engineering, 133 (8), pp. 955-963
[10] Kuo J.T., Hsu Y.C., Tung Y.K., Yeh  K.C. and Wu J.D., (2008). "Dam overtopping risk assessment considering inspection program", Stochastic Environmental Research and Risk Assessment, 22 (3), pp. 303-313.
[11] Kwon, H.H and Moon Y. (2006). "Improvement of overtopping risk evaluations using probabilistic concepts for existing dams", Stoch. Environ. Res. Risk Assess., 20, pp. 223-237.
[12] Lee H.L and Mays L.W. (1986). "Hydraulic uncertainties in flood levee capacity", Journal of Hydraulic Engineering, Vol. 112, No. 10, pp. 928-934.
[13] LianY. and Yen B.C. (2003). "Comparison of Risk calculation methods for a culvert", Journal of Hydraulic Engineering, Vol. 129, No. 2, pp. 140-152.
[14] Paik K. (2008). "Analytical derivation of reservoir routing and hydrological risk evaluation of detention basins", Journal of Hydrology, 352, pp. 191-201.
[15] Sharafati A., Zahabiyoun B. (2012). "Uncertainty analysis of storm pattern on Seymareh catchment", The international conference on Dam and Hydropower, Iran, Tehran
[16] Thompson K.D. Stedinger J.R. and Heath D.C. (1997). "Evaluation and presentation of dam failure and flood risks", Journal of Water Resources Planning and Management, 123 (4), pp. 216-227.
[17] USACE )1998(. HEC-1 flood hydrograph package users manual. Davis C.A: Hydrologic Engineering Centre.
[18] Yanmaz A.M. (2000). "Overtopping risk assessment in river diversion facility design", Canadian Journal of Civil Engineering 27(2). pp. 319-326
[19] Yenigun K. and Erkek C. (2007). "Reliability in dams and the effects of spillway dimensions on risk levels", Water Resources Management , Vol. 21, No. 4, pp. 747-760.
[20] Zhao B., Tung Y.K., Yeh K.C. and Yang. J.C. (1997). "Reliability analysis of hydraulic structures considering unit hydrograph uncertainty", Stochastic Hydrology and Hydraulics, 11, pp.
[21] شرافتی، ا. ذهبیون، ب. (139۱). "تولید استوکستیک هیدروگراف سیلاب در حوضه آبریز سد جامیشان" فصلنامه علمی-پژوهشی علوم و تکنولوژی محیط زیست، دوره 14، شماره 4. ص‌ص. 63-71
شرافتی، ا. ذهبیون، ب. (139۱). "تحلیل عدم قطعیت برآورد سیلاب توسط مدل HEC-HMS در حوضه آبریز سد جامیشان"، مجله علمی-پژوهشی هیدرولیک-دوره 7، شماره یک. ص‌ص. 13-28